The basic purpose of this research is to provide information on how the primate brain comes to be assembled, so as to provide a basis for understanding and treating the diseases of the nervous system that arise before birth. Work on the embryonic and fetal brain directly in monkey is essential for structures which have reached the peak of development in primates. The fetal brains are processed by several specialized cytological methods including autoradiography, Golgi staining, electronmicroscopy, histochemistry and manipulation of development by intrauterine neurosurgery. Attention is given to the interactions of brain cells as they proliferate and migrate relative to one another at early stages of development and as post-migratory neurons develop their dendritic and axonal processes and establish synaptic connections that ultimately attain "wiring" arrangements of the mature brain. Consequences of selective destruction of various brain centers and/or pathways sustained prenatally are evaluated in postnatal monkeys to determine the extent of neuronal plasticity. The projects ccurrently under study concern: (1) Histogenesis and synaptogenesis of the hippocampal formation; (2) time of neuron origin, neuronal differentiation including synaptogenesis of the neostriatum; (3) kinetics of proliferation of radial glial cells and their transformation into astrocytes; (4) neurogenesis of the spinal cord with particular emphasis on synaptogenesis of the substantia Rolandi; (5) development of deep cerebellar nuclei; (6) Dynamics and mechanism of cell migration in the primate telencephalon.